Apparatus for starting and controlling discharge devices



P 1944- w. J. KARASH 2,358,810

APPARATUS FOR STARTING AND CONTROLLING DISCHARGE DEVICES Filed April 21,1942 Inventor": Walter J. Karash 8 His Attorn gq.

Patented Sept. 26, 1944 APPARATUS FOR STARTING AND CONTROL- LINGDISCHARGE DEVICES Walter J. Karash, Annapolis, Md.. assignor to GeneralElectric Company, a corporation of New York Application April 21, 1942,Serial No. 439,820

9 Claims. (01. 315-188) My invention relates to apparatus for startingand controlling electric discharge devices such as discharge lamps ofthe fluorescent type which are now coming into common use. It relatespar ticularly to apparatus for starting a plurality of similar electricdischarge devices connected to be operated in series from a source ofcurrent supply. As at present constructed a lamp of that type comprisesa long transparent tubular envelope containing mercury vapor at a lowpressure and having its side walls coated with a suitable phosphor whichunder the influence of an electric discharge through the mercury vaporproduces fluorescence. The lamp electrodes which are mounted in the endsof the envelope are filamentary in form and are coated with a suitableelectron emissive material. Such a lamp requires for its starting the application of a voltage or electric impulse considerably higher than thevoltage necessary to keep the lamp in operation after it has beenstarted. A preheating of the electrodes of such lamps as they have beenconstructed heretofore has been essential in order to avoid excessivedamage to the electrodes by the starting voltage and the attendantblackening of the lamp walls in the vicinity of the electrodes by thematerial knocked ofi them. By reason of recent developments made in suchlamps particularly in the construction of their electrodes prior heatingof the electrodes is not as essential to the prevention of injury to thelamp as heretofore; Because of the desire to avoid the time delayoccasioned by electrode preheating, notwithstanding the fact that lampsas heretofore constructed were known to be seriously injured by beingcontinually started without electrode preheating, apparatus has beenused which would produce a voltage peak or impulse sufficiently high tomake the lamp break down immediately upon its application thereto.

It is an object of my invention to provide improved apparatus forstarting a plurality of similar electric discharge devices connected tobe operated in series from a source of current supply whose voltage notonly is less than the sum of the starting voltages of the devices but isless than the starting voltages of the individual devices.

My invention will be better understood from the following descriptiontaken in connectionwith the accompanying drawing and its scope will bepointed out in the appended claims.

Referring to the drawing, Figs. 1 to inclusive are circuit diagramsillustrating various embodiments of my invention.

In Fig. 1 two long tubular similar discharge devices which, for example,may be 40 watt fluorescent lamps are shown diagrammatically at I and 2each provided with filamentary electrodes 3 5 ;which may or may not beshort-circuited as shown by the drawing. The lamps I and 2 when startedwithout any preheating of their electrodes may each require from 400 to450 volts to start depending upon various conditions such as thegeometry of the envelope and the temperature of the ambient. Theenvelopes of the lamps contain mercury vapor at low pressure and theside walls thereof have a phosphor thereon which when excited by adischarge through the mercury vapor produces fluorescence. The two lampsare connected to be operated in series from the secondary of theauto-transformer 5, the voltage of which secondary may, for example, be360 volts, and the connection includes the ballast reactor 6 whosereactance may be 560 ohms. The transformer has its primary connectedthrough the control switch 8 with the source 9 of alternating currentsupply which, for example, may be a 115 volt, cycle lighting circuit.

Inasmuch as the combined starting voltage of the two lamps in series isconsiderably higher than the secondary voltage of the transformer 5 itwill be seen that the lamps when connected in series with thetransformer, as shown, will not start without aid of other apparatus butafter having been started they will continue to operate in series.Moreover, the voltage of the transformer is less than the startingvoltage of either lamp. To effect the starting of the lamps, I haveprovided the circuit l2 shunting the lamp 2 and comprising the capacitorl3 and the winding 14 whose reactive impedances may be 5300 and 2860ohms, respectively. The net reactance of the shunt circuit therefore iscapacitive and the net reactive voltage of that circuit is opposite incharacter to the reactive voltage of the ballast 6. The winding I4 isthe secondary winding of the transformer I5 whose primary winding I6 isloosely coupled with the winding I4 and may, for example, have a 1:1turn ratio therewith. The primary Winding I6 is shown connected acrossthe primary of the auto transformer 5,

hence is connected, through the switch 8 with the source of currentsupply 9. The winding l6 may, however, be connected across the secondaryof the transformer 5 or across any desired portion thereof. By reason ofthe shunt circuit l2 substantially the full voltage of the transformer 5to which is added the voltage of the secondary H of the transformer I5is applied to the lamp I and that combined voltage, which may beapproximately 4'75 volts, is sufficient to cause a discharge to starttherein. After that lamp has started the current taken by it flowsthrough the mediately starts and the current taken thereby traverses theballast reactor I5 and the shunt circuit comprising the capacitor I3 andthe winding I4. The resulting voltage then applied to the lamp 2 by theshunt circuit causes that lamp also to start. After it has started itprovides a relatively low impedance path in shunt with the circuit I2.The two lamps I and 2 thereafter continue to operate connected in seriesacross the secondary of the transformer 5 and since the ballast 6 isinductive the lamp current will be lagging. If it is desired that theenergy taken from the source 9 shall be at approximately unity powerfactor one may connect a suitable capacitor represented at 4 across thesecondary of the transformer.

In Fig. 2 the lamps I and 2, the transformer 5, and the transformer I5are similar to the abovedescribed corresponding parts of Fig. 1.However, in this case the lamps operate with a leading current. The lampballast in Fig. 2 comprises the reactor I1 and the capacitor I8, thereactive impedances of which may for example be 630 and 1330 ohmsrespectively, and since the impedance of the capacitor is greater thanthat of the reactor the lamp circuit is capacitive. To effect thestarting of the lamps I have provided the circuit I2 which shunts thelamp 2 and which comprises the reactor I9 and the secondary winding I4of the transformer I5. This transformer unlike the transformer I5 ofFig. 1 has its primary and secondary windings closely coupled. Thecombined reactive impedances of the reactor I9 and the winding I4 may,for example, be 3000 ohms. The reactance of the shunt circuit in thiscase therefore is inductive and the reactive voltage of that circuit isopposite in character to the net reactive voltage of the reactor I1 andthe capacitor I8 which comprise the ballast. The lamps I and 2 arestarted in a manner similar to that described above in connection withFig. 1, lamp I first being started by reason of the combined voltage ofthe transformers 5 and I5 applied across it and after it has started,the lamp 2 being started by reason of the voltage of the shunt circuitI2 being applied to it. The two lamps I and 2 thereafter continue tooperate connected in series across the secondary of the transformer 5and since the ballast is capacitive the lamp current will be leading.If, in this form of my invention,, it is desired that the energy takenfrom source 9 shall be at approximately unity power factor one mayconnect a suitable reactor, as illustrated at 20, across the primary ofthe transformer 5 or, if preferred, he may con struct the core of thetransformer with an air gap therein thereby to increase the excitingcurrent of the transformer.

In hat form of my invention illustrated by Fig. 3 the transformers 5 andI5 or I5 of the forms illustrated by Figs. 1 and 2 are combined in thesingle transformer 22 having two secondary parts one shown at 23, abovethe-tap 24 and one shown at 25 below the tap 24. That part 23 of thetransformer by which voltage, for example 360 volts, is applied to thetwo lamps in series corresponds to and is connected with the source ofsupply in a manner similar to that of the transformer 5 in Fig. l. Theadditional voltage which in the case of Fi 1 was obtained from thesecondary winding I4 is in the case of Fig. 3 obtained from thesecondary part 25, the voltage of which may, for example, be 240 volts.The circuit which shunts the lamp 2 in this case includes the capacitor26, the reactor 21 and the secondary part 25, the reactances of whichcapacitor and reactor may,.; for example, be 5300 and 2400 ohmsrespectively. Inasmuch as the lamps in that form of my inventionillustrated by Fig. 3 start in a manner similargtothat described abovein connection with Fig. 1, it is thought to be unnecessary to include adescription of how they start.

In that form of my invention as shown by Fig. 4 a single transformer isemployed as in Fig. 3 but the transformer has a special form. Itcomprises the core 29 having the primary winding 30 which connectsthrough the switch 8 with the source 9 and the secondary winding 3|provided with the tap 32 which divides tl.e winding into the twosecondary parts 33 and 34. The core of the transformer has the magneticshunt 35 and that leg thereof carrying the secondary winding 3I has thebridge gap 36 therein. The voltage which is applied to the two lamps inseries is the voltage of the secondary part 33, which may be 240 volts,plus the voltage of the source 9 which if volts will be approximately355 volts which is insufficient to start the lamps in series or to starteither lamp alone. The lamp I connects across the source of supply 9through the entire secondary winging 3|, the voltage of which may 475,and the reactor 31 and the ballast capacitor 38. By reason of theseconnections the lamp I may have applied to it approximately 590 voltsand hence will be started.

After the lamp I starts the part 34 of the secondary 3| and the reactor31 forms a shunt circuit about the lamp 2, and the reactive voltage ofthis shunt circuit being inductive is opposite to the reactive voltageof the ballast capacitor 38. The combined voltage due to the inductivereactance of this shunt circuit together with the voltage induced in thepart 34 is sufficient to cause the lamp 2 to start. After the two lampshave been thus started they operate in series wih a -leading current.

That form of my invention illustrated by Fig. 5 employs the transformer22' which is similar in construction and in the manner in which it isconnected with the source to the transformer 22 in Fig. 3. The circuitincludes two pairs of series connected lamps I, 2 and I, 2 which aresupplied by the same transformer 22', the circuits of the two pairs oflamps being in effect a combination of the circuits shown in Figs. 2 and3, the one circuit, namely that of the lamps I and 2, having a leadingcurrent and the other circuit, namely that of lamps I and 2 having alagging current. Ballast for the leading circuit comprises the reactorI1 and the capacitor I8 which members may be similar to the membershaving the same numbers in Fig. 2 and ballast for the lagging circuitcomprises the reactor 6 which may be similar to the member having thesame number in Fig. 3. The circuit shunting the lamp 2 includes thereactor I 9 and the secondary part 25 which may be similar respectivelyto the reactor l9 and the winding I4 in Fig. 2 and the circuit shuntingthe lamp 2' includes the capacitor 26, the reactor 21 and the secondarypart 25 which members may be similar to the members having the samenumbers in Fig. 3. Inasmuch as the circuits shown in Fig. function insubstantially the same manner to start the lamps, as has already beendescribed in connectionwith Figs. 2 and 3, it is thought to beunnecsssary to again describe the operation of these circuits In any ofthe above described forms of my invention if it is desired that thecurrents taken by the two lamps be more nearly equal during theiroperation and also if greater stability of the lamps be desired one maybuild into the reactor.

or other winding included in the circuit shunting the lamp 2 or bothlamps 2 and 2 in the case of the form shown in Fig. 5 somewhat moreresistance than would otherwise be employed or, if preferred, he mayinsert a separate small resistor in that circuit.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, a plurality of electric discharge devices, meanshaving reactive impedance for connecting said devices to be operated inseries from a source of alternating current whose voltage is less thanthe sum of the starting voltages of said devices, and a reactive circuitconnected across one of said devices, the reactive voltage of saidcircuit being opposite in character to the reactive voltage of saidimpedance, and means in said circuit arranged to be energized from saidsource for increasing the voltage across said circuit to cause anotherof said devices to start.

2. In combination, a plurality of electric discharge devices, meanshaving reactive impedance for connecting said devices to be operated inseries from a source of alternating current whose voltage is less thanthe sum of the starting voltages of said devices, and a reactive circuitconnected across one of said devices, the reactive voltage of saidcircuit being opposite in character to the reactive voltage of saidimpedance, said circuit including a winding, and means arranged to beenergized from said source for inducing a voltage in said winding toincrease the voltage applied by'said source to another of said devices.

3. In combination, a plurality of electric discharge devices, a step-uptransformer, means having reactive impedance connecting said devices tobe operated in series and energized from the secondary of saidtransformer, the voltage of which secondary is less than the sum of thestarting voltages of said devices, a second transformer, and a reactivecircuit including the secondary of said second transformer connectedacross one of said devicw, the reactive voltage of said circuit beingopposite in character to that of said impedance.

4. In combination, a plurality of electric discharge devices, a step-uptransformer the primary of which is adapted to be connected with asource of alternating current supply, reactive means whose net reactanceis capacitive connecting said devices to be operated in series from thesecondary of said transformer, a separate transformer having its primaryand secondary windings closely coupled with each other and its primaryconnected with the primary of said stepup transformer, and an inductivereactive circuit including the secondary of said separate transformerconnected across one of said devices.

5. In combination, a plurality of electric discharge devices, a step-uptransformer, means having reactive impedance connecting said devices tobe operated in series and energized from the secondary of saidtransformer the voltage of which secondary is less than the sum of thestarting voltages of said devices, said transformer having an additionalsecondary, and a reactive circuit including said additional secondaryconnected across one of said devices, the reactive voltage of saidcircuit being opposite in character to that of said impedance.

6. In combination, a plurality of electric discharge devices, a step-uptransformer having a plurality of secondary parts, inductive reactivemeans connecting said devices in series across one of said secondaryparts, the voltage of said one part being less than the sum of thestarting voltages of said devices, and a capacitive reactive circuitincluding another of said secondary parts connected across one of saiddevices.

7. In combination, a plurality of electric discharge devices, a step-uptransformer having a plurality of secondary parts, capacitive reactivemeans connecting said devices in series across one of said secondaryparts, the voltage of said one part being less than the sum of thestarting voltages of said devices, and an inductive reactive circuitincluding another of said secondary parts connected across one of saiddevices.

8. In combination, a plurality of similar electric discharge devices,means having reactive impedance for connecting said devices to beoperated in series from a source of alternating current whose voltage isless than the starting voltage of each of said devices, and a circuitconnected across one of said devices including means for increasing thevoltage applied by said source to another of said devices to cause it tostart and including reactive means, the reactive voltage of which isopposite in character to that of said first mentioned means, for causingsaid one device subsequently to start.

9. In combination, a plurality of similar electric discharge devices,means having reactive impedance for connecting said devices to beoperated in series from a source of alternating current whose voltage isless than the starting voltage of each of said devices, and a circuitconnected across one of said devices including other reactive meanstogether with means arranged to be energized from said source forraising the voltage applied to the other of said devices from saidsource, to cause it to start, the reactive voltone device is caused tostart.

WALTER J.

